linux-kernel - [PATCH 3/3] x86,idle: Set residency to 0 if target Cstate not really enter

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Date:	Fri, 11 May 2012 11:15:57 -0400
From:	Youquan Song <youquan.song@...el.com>
To:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org, len.brown@...el.com,
	akpm@...ux-foundation.org
Cc:	arjan@...ux.intel.com, len.brown@...ux.intel.com,
	suresh.b.siddha@...el.com,
	Youquan Song <youquan.song@...ux.intel.com>,
	Youquan Song <youquan.song@...el.com>
Subject: [PATCH 3/3] x86,idle: Set residency to 0 if target Cstate not really enter

When cpuidle governor choose a C-state to enter for idle CPU, but it notice that
there is tasks request to be executed. So the idle CPU will not really enter
the target C-state and go to run task.

In this situation, it will use the residency of previous really entered target 
C-states. Obviously, it is not reasonable. 

So, this patch fix it by set the target C-state residency to 0. 

Signed-off-by: Youquan Song <youquan.song@...el.com>
---
 drivers/cpuidle/cpuidle.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)


diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 2f0083a..7992417 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -136,6 +136,10 @@ int cpuidle_idle_call(void)
 	/* ask the governor for the next state */
 	next_state = cpuidle_curr_governor->select(drv, dev);
 	if (need_resched()) {
+		dev->last_residency = 0;
+		/* give the governor an opportunity to reflect on the outcome */
+		if (cpuidle_curr_governor->reflect)
+			cpuidle_curr_governor->reflect(dev, next_state);
 		local_irq_enable();
 		return 0;
 	}
--
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